i6 



INSECTS. 



becoming pupae, and a little later in May emerging as full-grown saw-flies. The 

 parasitic insect {Pachymerus calcitrator) figured in the illustration on p. 15 is one of 

 the Petiolate Hymenoptera which seems to be exclusively parasitic on the present 

 species. 



Tailed Wasps, — Family Siricid^e. 



In this family the female is furnished with a long, boring ovipositor for 

 piercing the bark of trees ; the eggs being laid in the orifice thus formed, and the 

 larvae feeding on the wood. In the accompanying illustration of the boring 

 apparatus of one species c, c, a, shows the whole of the muscular structure with 



which the boring is carried out. The perfect insects are 

 usually of large size and conspicuously coloured. Among 

 the typical forms the common tailed-wasp (Sirex juvencus) 

 is a very rare species in England, although more plentiful 

 on the Continent. The females, which are sometimes 

 surprised in the act of depositing their eggs on pine-trees, 

 may be easily caught, as the ovipositor can only be with- 

 drawn with considerable difficulty. Indeed, the abdomen 

 breaks in half, if the insect be roughly grasped. The much 

 larger giant tailed-wasp (S. gigas) is far commoner among 

 pine-trees, and is distinguished by its bands of black and 

 yellow. Although it does considerable damage, it does not 

 attack a perfectly healthy tree, unless recently felled. How 

 long the larvae may live in the interior of the tree, and 

 how long it is before the perfect insect appears, is not 

 known, but cases are often quoted of this insect appearing 

 in houses soon after their completion, having evidently 

 emerged from the wood of the joists and beams. Another 

 genus is well represented by the broad -bodied saw-fly 

 (Lyda campestris). In this species the grubs feed on the 

 young shoots of the Scotch fir, in which the eggs are laid. 

 When hatched, the larvae spin a slight web in which they 

 remain concealed, protruding the forepart of the body 

 when feeding on the pine needles. When all the needles in the neighbourhood 

 have been devoured, the web is extended, so that a great number of young shoots 

 may be embraced and destroyed. The perfect insect is shining blue-black, with 

 some of the abdominal segments reddish yellow. 



BORING APPARATUS OF GIANT 



tailed wasp (much en 

 larged). 



True Saw-Flies— Family Tenthredinid^:. 



In this exceedingly numerous and widely distributed group, a well known 

 example is the pine saw-fly (Lophyrus pini), of which the larvae are sometimes 

 found in such numbers in pine-woods, where they feed upon the needles, that the 

 trunks are often coloured yellow and the branches weighed down. Towards 

 the end of July, the perfect insect emerges by gnawing off the cap of the barrel- 

 shaped pupa-case. The eggs are laid in incisions made in the needles, these 



